This application claims the benefit of Japanese Patent Application No. 2002-103469, incorporated herein by reference.
The present invention relates to an apparatus and method for attaching an undercover to the underside of a floor panel of a car body. In particular, the present invention relates to an undercover attaching apparatus and method using studs fixed at predetermined positions on the underside of a floor panel of a car body, mounting holes formed in an undercover to receive the respective studs therein, and stud-engaging fasteners attached to the undercover in respective mounting holes.
It is well known to attach an undercover to the underside of a floor panel of a car body, for example, as disclosed in Japanese Utility Model Laid-Open No. 59129676.
In one technique of attaching an undercover to the underside of a floor panel of a car body, a plurality of threaded studs are fixed at predetermined positions of the underside of the floor panel, and a plurality of mounting holes are formed at predetermined positions of the undercover to receive the respective studs therein. Then, the undercover is positioned to the underside of the floor panel to insert the studs into the corresponding mounting holes, and nuts are screwed onto the respective studs with a tool or the like to complete an operation for attaching the undercover to the underside of the floor panel. This operation is troublesome and time-consuming because of the need for fastening a number of nuts to the studs over a large area of the undercover.
Further, when the undercover is attached to the underside of the floor panel by tightly screwing the nuts onto the threaded studs to prevent the undercover from dropping off, a fastening stress is concentrated on the fastened regions. The undercover is commonly a panel made of plastic material, which tends to expand and contract due to temperature changes during engine running and cooling down. Since the undercover is tightly fastened by the nuts at predetermined positions, it is subject to being distorted by thermally-induced stress around the fastened regions. This problem could be avoided if reliable attachment of an undercover could be achieved while allowing the attached undercover to be displaced along the underside of the floor panel to permit thermal expansion and contraction.
Japanese Utility Model Laid-Open No. 62-59311 (Japanese Utility Model Publication No. 3-19603) discloses an attaching assembly for attaching a panel such as an insulating panel, but not an undercover. In this attaching assembly, a tubular member is disposed around a stud in advance to position a panel, and a clip is engaged with the stud, so that the clip can be coaxially attached to the stud to maintain a high fixing force stably. If this attaching assembly were used to attach an undercover, it would be necessary to perform a troublesome operation of attaching a plurality of tubular members to corresponding studs in advance, and there would be no assurance of avoiding thermally-induced distortions.
Japanese Utility Model Laid-Open No. 7-41035 (Japanese Utility Model Registration No. 25843861) discloses a two-component component clip for attaching a flexible panel such as a trim panel to a car body. In this clip, a first component has a hollow shank into which a hollow base of a second component is previously fitted to assemble the first and second components together, and the resulting assembly is inserted into and attached to the flexible panel from one side thereof. If this clip were applied to an undercover, however, it could not be inserted into the undercover from one side thereof, because the undercover has a high rigidity and is different from a flexible trim panel.
Japanese Utility Model Laid-Open No. 8-001091 (Japanese Utility Model Registration No. 2577997) discloses a two-component clip for attaching a panel to a car body. This clip comprises a male component with a flange and a female component with a flange. The male and female components are inserted into a mounting hole of the panel from opposite sides of the panel, respectively, to couple them together so as to clamp the panel therebetween. Then, the clip is engaged with a stud to fix the panel to the car body. There is no suggestion in Japanese Utility Model Laid-Open No. 8-001091 of applying this clip to the attachment of undercovers. In addition, Japanese Utility Model Laid-Open No. 8-001091 does not include any suggestion of a structure that would avoid thermally-induced distortion.
It is therefore an object of the present invention to provide an undercover attaching apparatus and method that facilitate attaching an undercover and that allow the attached undercover to be desirably displaced along the underside of a floor panel due to thermal expansion and contraction, thereby avoiding thermally-induced distortion.
According to the present invention, studs are fixed at predetermined positions of the underside of a floor panel, mounting holes are formed in the undercover to receive the studs therein, and tubular fasteners are attached to the undercover in the mounting holes. Then, the fasteners are engaged with respective studs.
In one non-limiting embodiment of the invention, the fastener comprises a first clip including an outer tubular portion adapted to be inserted into the mounting hole of the undercover; and a second clip including an inner tubular portion adapted to be inserted into the outer tubular portion of the first clip, and an engagement member such as a pawl or pawls adapted to be engaged with the stud. The first clip is formed with a first flange adapted to be brought into contact with one side of the undercover when the outer tubular portion is inserted into the mounting hole; the second clip is formed with a second flange adapted to be brought into contact with the other surface of the undercover when the inner tubular portion is inserted into the outer tubular portion; and the outer and inner tubular portions are formed with first and second coupling portions for coupling the outer and inner tubular portions to one another, whereby when the outer tubular portion is inserted into the mounting hole of the undercover and then the inner tubular portion is inserted into the outer tubular portion to couple the first and second clips together by the coupling portions, the first and second flanges are brought into contact with respective sides of the undercover around the periphery of the mounting hole to clamp the undercover therebetween. The mounting hole of the undercover has a diameter substantially larger than the outer diameter of the outer tubular portion, providing diametral clearance that allows the undercover to be displaced along the underside of the floor panel due to its thermal deformation, and the first and second clips are formed to allow the first and second flanges to clamp the undercover therebetween with a predetermined clamping force capable of clamping the undercover without its wobbling movement in the axial direction of the stud while allowing the undercover to be displaced along the underside of the floor panel due to thermal deformation.
In the preferred method of the invention, the fasteners are fastened to the undercover in advance of installing the undercover on a floor panel, making it possible to readily carry the undercover with the fasteners held thereon. Thus, the undercover can be attached to the underside of the floor panel of a car body by a simple attaching operation of properly positioning the undercover with the fasteners to the underside of the floor panel and then pressing the undercover to the underside of the floor panel while inserting the studs into the fasteners. Further, the first and second clips are formed so that the first and second flanges clamp the undercover therebetween with a predetermined clamping force that prevents wobbling movement of the undercover in the axial direction of the studs while allowing the undercover to be displaced along the underside of the floor panel due to its thermal deformation, and thereby to eliminate distortion of the undercover around the studs.
Preferably, the studs are threaded studs, and in one embodiment the second clip includes the inner tubular portion having a stud engagement pawl or pawls formed in the inside thereof; the second flange is formed at one of the ends of the inner tubular portion, and a polygonal tubular portion extends from the second flange as an extension of the inner tubular portion. This polygonal tubular portion may be formed as a tubular body having an inner diameter greater than the outer diameter of the thread of the stud, so as to allow the polygonal tubular portion to be free from engagement with the thread of the stud. The polygonal tubular portion can be rotated about the axis of the stud by a tool, so as either to provide tighter fastening of the engagement pawl on the stud or to release the fastening.
The second flange may have an outer edge formed to extend toward the other end of the inner tubular portion so as to allow the second flange to be brought into contact with one side of the undercover only at the outer edge, to facilitate maintaining the predetermined clamping force. Further, the first flange may have a flat plate shape capable of being brought into contact with the other surface of the undercover in its entirety.
Furthermore, a portion of the outer tubular portion may be divided by axially extending slits to form a first coupling portion of the first clip, and the outer surface of the inner tubular portion can be formed with a second coupling portion adapted to be engaged with the first coupling portion. The first and second coupling portions are formed to allow the first and second flanges to be spaced apart from each other by an axial distance equal to or slightly less than the thickness of the undercover so as to provide a predetermined clamping force when the first and second coupling portions are engaged with one another.
In a second non-limiting embodiment of the invention, the studs may be threaded studs, and the second clip may include the inner tubular portion having a stud-engagement pawl or pawls formed in the inside thereof; the second flange may be formed at one of the ends of the inner tubular portion, and a polygonal tubular portion may extend from the second flange as an extension of the inner tubular portion. This polygonal tubular portion has an inner diameter less than the outer diameter of the thread of the stud, so as to allow the polygonal tubular portion to be engaged with the thread of the stud. The polygonal tubular portion can be rotated about the axis of the stud by a tool, so as to allow the polygonal tubular portion to be threaded by the stud and to be either threadedly engaged with the stud or to release the threaded engagement with the stud. According to this embodiment, the stud-engagement pawl of the second clip can be used for a temporary fastening, and a tight final fastening can be achieved by a combination of the engagement of the stud-engagement pawl and the threaded engagement of the polygonal tubular portion.
The first flange may be formed at one of the ends of the outer tubular portion of the first clip. This first flange preferably has an outer edge formed to extend toward the other end of the outer tubular portion so as to allow the first flange to be brought into contact with one side of the undercover only at the outer edge to facilitate maintaining the predetermined clamping force. The second flange may have a flat plate shape capable of being brought into contact with the other surface of the undercover in its entirety.
Further, a portion of the outer tubular portion may be divided by axially extending slits to form a first coupling portion of the first clip for engaging a second coupling portion of the second clip. The first and second coupling portions are formed to allow the first and second flanges to be spaced apart from one another by an axial distance equal to or slightly less than the thickness of the undercover so as to provide a predetermined clamping force when the first and second coupling portions are engaged with one another.
Furthermore, the inner tubular portion of the second clip may have an axial length which allows the first flange to be brought into contact with the underside of the floor panel and allows the second flange to press the undercover, when an end of the inner tubular portion is brought into contact with the underside of the floor panel by the rotation of the polygonal tubular portion. According to this structure, the undercover can be firmly attached to the underside of the floor panel while limiting the clamping force to within a certain range that allows the undercover to be displaced along the underside of the floor panel due to thermal deformation.